My wife used to work in Dental Services for the NHS. Everyone in her department (who oversaw licences, criminal record checks and NHS contracts) made a point of addressing all dentists as Mr. X.
Some of them would try and insist on being called Dr. X at which point it would be pointed out that they didn't have a PhD or a medical degree and as such were not Doctors.
Technically a dentist who calls himself Dr. may be committing a criminal offence. If their intention is to make people think they are a Doctor then they are.